Generating physio-realistic avatars for training non-contact models to recover physiological characteristics

ABSTRACT

Systems and methods are provided that are directed to generating video sequences including physio-realistic avatars. In examples, an albedo for an avatar is received, a sub-surface skin color associated with the albedo is modified based on physiological data associated with physiologic characteristic, and an avatar based on the albedo and the modified sub-surface skin color is rendered. The rendered avatar may then be synthesized in a frame of video. In some examples, a video including the synthesized avatar may be used to train a machine learning model to detect a physiological characteristic. The machine learning model may receive a plurality of video segments, where one or more of the video segments includes a synthetic physio-realistic avatar generated with the physiological characteristic. The machine learning model may be trained using the plurality of video segments. The trained model may be provided to a requesting entity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/907,110, filed on Jun. 19, 2020, the entiredisclosure of which is hereby incorporated by reference for allpurposes.

BACKGROUND

Collecting high-quality physiological data presents numerous challenges.First, recruiting and instrumenting participants is often expensive andrequires advanced technical expertise which severely limits itspotential volume. This is especially true for imaging-based methods asthey require recording and storing video content. Second, trainingdatasets that have already been collected may not contain the types ofmotion, illumination changes or appearances that feature in theapplication context. Thus, a model trained on these data may be brittleand not generalize well. Third, the data can reveal the identity of thesubjects and/or sensitive health information. For imaging methods thisis exacerbated by the fact that most datasets of video recordingsinclude the subjects face in some or all of the frames. It is withrespect to these and other general considerations that the aspectsdisclosed herein have been made. Also, although relatively specificproblems may be discussed, it should be understood that the examplesshould not be limited to solving the specific problems identified in thebackground or elsewhere in this disclosure.

SUMMARY

In accordance with examples of the present disclosure, synthetic datamay be used to train physiological sensing systems, therebyside-stepping the challenges associated with recruiting andinstrumenting participants, limited training data containing varioustypes of motion, illumination changes or appearances, and identityprotection. Once a computer graphics pipeline is in place, generation ofsynthetic data is much more scalable than recording videos ascomputation is relatively inexpensive and can be procured at will usingcloud computing. In addition, rare events or typically underrepresentedpopulations can be simulated in videos, with the proper knowledge of thestatistical properties of the events or a set of examples. Furthermore,synthetic datasets would not need to contain faces or physiologicalsignals with the likeness of any specific individual. Finally,parameterized simulations would systematically vary certain variables ofinterest (e.g., velocity of motion or intensity of the illuminationwithin a video) which is both useful to train more robust methods aswell as evaluating performance under different conditions.

In accordance with examples of the present disclosure, high-fidelityphysio-realistic computer simulations may be utilized to augmenttraining data that can be used to improve non-contact physiologicalmeasurements.

In accordance with at least one example of the present disclosure, amethod for generating video sequences including physio-realistic avatarsis provided. The method may include receiving an albedo for an avatar,modifying a sub-surface skin color associated with the albedo based onphysiological data associated with physiologic characteristic, renderingan avatar based on the albedo and the modified sub-surface skin color,and synthesizing a frame of video, the frame of video including theavatar.

In accordance with at least one example of the present disclosure, asystem for training a machine learning model using video sequencesincluding physio-realistic avatars is provided. The system may include aprocessor, and memory storing instructions, which when executed by theprocessor, cause the processor to receive a request from a requestingentity to train a machine learning model to detect a physiologicalcharacteristic, receive a plurality of video segments, wherein one ormore of the video segments includes a synthetic physio-realistic avatargenerated with the physiological characteristic, train the machinelearning model with the plurality of video segments, and provide atrained model to the requesting entity.

In accordance with at least one example of the present disclosure, acomputer-readable media is provided. The computer-readable mediaincludes instructions, which when executed by a processor, cause theprocessor to receive a request to recover a physiological characteristicfrom a video segment, obtain a machine learning model trained withtraining data that includes physio-realistic avatars generated with thephysiological characteristic, receive a video segment, identify ameasure associated with the physiological characteristic from the videosegment using the trained machine learning model, and provide anassessment of the physiological characteristic to the requesting entitybased on the measure.

Any of the one or more above aspects in combination with any other ofthe one or more aspects. Any of the one or more aspects as describedherein.

This Summary is provided to introduce a selection of concepts in asimplified form, which is further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Additionalaspects, features, and/or advantages of examples will be set forth inpart in the following description and, in part, will be apparent fromthe description, or may be learned by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive examples are described with reference tothe following Figures.

FIG. 1 depicts first details directed to generating physio-realisticavatar videos in accordance with examples of the present disclosure;

FIG. 2 depicts details directed to rendering and synthesizing videoframes including physio-realistic avatars in accordance with examples ofthe present disclosure;

FIG. 3 depicts second details directed to generating physio-realisticavatar videos in accordance with examples of the present disclosure;

FIG. 4 depicts details directed to training a machine learning model inaccordance with examples of the present disclosure;

FIG. 5 depicts an example rendering of an avatar that includes aphysiological data signal in accordance with examples of the presentdisclosure;

FIG. 6 depicts details directed to using a trained machine learningmodel to recover a physiological signal in accordance with examples ofthe present disclosure;

FIG. 7 depicts an example graph including waveforms and power spectrumsfor isolation or otherwise determining a physiological signal inaccordance with examples of the present disclosure;

FIG. 8 depicts details of a physio-realistic video and/or modelgenerator in accordance with examples of the present disclosure;

FIG. 9 depicts a method directed to generating a physio-realistic avatarvideo in accordance with examples of the present disclosure;

FIG. 10 depicts a method directed to training a machine learning modelin accordance with examples of the present disclosure;

FIG. 11 depicts a method directed to generating and/or locating aphysio-realistic avatar video in accordance with examples of the presentdisclosure;

FIG. 12 depicts a method directed to using a trained machine learningmodel to recover a physiological signal in accordance with examples ofthe present disclosure;

FIG. 13 depicts block diagram illustrating physical components (e.g.,hardware) of a computing device with which aspects of the disclosure maybe practiced;

FIG. 14A illustrates a first example of a computing device with whichaspects of the disclosure may be practiced;

FIG. 14B illustrates a second example of a computing device with whichaspects of the disclosure may be practiced; and

FIG. 15 illustrates at least one aspect of an architecture of a systemfor processing data in accordance with examples of the presentdisclosure.

DETAILED DESCRIPTION

In the following detailed description, references are made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustrations specific embodiments or examples. These aspects maybe combined, other aspects may be utilized, and structural changes maybe made without departing from the present disclosure. Embodiments maybe practiced as methods, systems or devices. Accordingly, embodimentsmay take the form of a hardware implementation, an entirely softwareimplementation, or an implementation combining software and hardwareaspects. The following detailed description is therefore not to be takenin a limiting sense, and the scope of the present disclosure is definedby the appended claims and their equivalents.

Photoplethysmography (PPG) is a non-invasive method for measuringperipheral hemodynamics and vital signals such as Blood Volume Pulse(BVP) via light reflected from, or transmitted through the skin. Whiletraditional PPG sensors are used in contact with the skin, recent workhas shown that digital imagers can also be used even at some distancefrom the body offering some unique benefits. First, for subjects withdelicate skin (e.g., infants in an NICU, burn patients or the elderly)contact sensors can damage their skin, cause discomfort, and/or increasetheir likelihood of infection. Second, cameras are ubiquitous (availableon many tablets, personal computers and cellphones) offering unobtrusiveand pervasive health monitoring. Third, unlike traditional contactmeasurement devices (e.g., a smart watch) remote cameras allow forspatial mapping of the pulse signal that can be used to approximatepulse wave velocity and capture spatial patterns in the peripheralhemodynamics.

While there are many benefits of non-contact PPG measurement (a.k.a.,imaging photoplethymography), this approach is especially vulnerable todifferent environmental factors posing relevant research challenges. Forinstance, recent research has focused on making iPPG measurements morerobust under dynamic lighting and motion, and characterizing andcombating the effects of video compression. Historically, iPPG methodsoften relied on unsupervised methods (e.g., independent componentanalysis (ICA) or principal component analysis PCA) or hand-crafteddemixing algorithms. Recently, supervised neural models have beenproposed providing state-of-the-art performance in the context of heartrate measurement. These performance gains are often a direct result ofthe model scaling well with the volume of training data; however, aswith many machine learning tasks the volume and diversity of theavailable data soon becomes the limiting factor.

As previously mentioned, it is difficult to collect high-qualityphysiological data for a number of reasons. First, recruiting andinstrumenting participants is often expensive and requires advancedtechnical expertise which severely limits its potential volume. This isespecially true for imaging-based methods as they require recording andstoring video content. Second, training datasets that have already beencollected may not contain the types of motion, illumination changes, orappearances needed to train a model. thus, a model trained on these datamay be brittle and not generalize well. Third, the data can reveal theidentity of the subjects and/or sensitive health information. Forimaging methods this is exacerbated by the fact that most datasets ofvideo recordings include the subjects face in some or all of the frames.

In accordance with examples of the present disclosure, synthetic datamay be utilized to train iPPG systems in order to overcome thepreviously mentioned challenges. Utilizing a graphics pipeline,synthetic data can be generated that is much more scalable thanrecording videos. In addition, generating synthetic data is relativelycomputationally inexpensive and can be performed using cloud computing.Rare events or typically underrepresented populations can be simulatedin videos and such simulated videos would not need to contain faces orphysiological signals with the likeness of any specific individual. Inaddition, parameterized simulations would provide a manner tosystematically vary certain variables of interest (e.g., velocity ofmotion or intensity of the illumination within a video) which is bothuseful to train more robust models as well as evaluate model performanceunder different conditions.

Camera-based vital sign measurement using photoplethysmography involvescapturing subtle color changes in skin pixels. Graphics simulationstarts by assuming there is a light source that has a constant spectralcomposition but varying intensity. Accordingly, the red, green, blue(RGB) values of the k-th skin pixel in an image sequence can then bedefined by a time-varying function:

C _(k)(t)=I(t)·(v _(s)(t)+v _(d)(t))+v _(n)(t)  Equation 1

C _(k)(t)=I(t)·(v _(s))+V _(abs)(t)+v _(sub)(t))+v _(n)(t)  Equation 2

where C_(k) (t) denotes a vector of the RGB color channel values; I(t)is the luminance intensity level, which changes with the light source aswell as the distance between the light source, skin tissue and camera;I(t) is modulated by two components in the DRM: specular (glossy)reflection v_(s)(t), mirror-like light reflection from the skin surface,and diffuse reflection v_(d)(t). The diffuse reflection in turn has twoparts: the absorption V_(abs)(t) and sub-surface scattering of light inskin-tissues V_(sub)(t); v_(n)(t) denotes the quantization noise of thecamera sensor. I(t), v_(s)(t) and v_(n)(t) can all be decomposed into astationary and a time-dependent part through a linear transformation:

v _(d)(t=u _(d) ·d ₀+(u _(abs) +u _(sub))·p(t)  Equation 4

where u_(d) denotes the unit color vector of the skin-tissue; d₀ denotesthe stationary reflection strength; v_(abs)(t) and v_(sub)(t) denote therelative pulsatile strengths caused by both changes in hemoglobin andmelanin absorption and changes in subsurface scattering respectively, asthe blood volume changes; p(t) denotes the BVP.

v _(s)(t)=u _(s)·(s ₀+Φ(m(t),p(t)))  Equation 5

where u_(s) is the unit color vector of the light source spectrum; s₀and Φ(m(t), p(t)) denote the stationary and varying parts of specularreflections; m(t) denotes all the non-physiological variations such asflickering of the light source, head rotation, facial expressions andactions (e.g., blinking, smiling).

I(t)=I ₀·(1+ψ(m(t),p(t)))  Equation 6

where I₀ is the stationary part of the luminance intensity, andI₀·ψ(m(t), p(t)) is the intensity variation observed by the camera. Theinteraction between physiological and non-physiological motions, Φ(·)and ψ(·), are usually complex non-linear functions. The stationarycomponents from the specular and diffuse reflections can be combinedinto a single component representing the stationary skin reflection:

u _(c) ·c ₀ =u _(s) ·s ₀ +u _(d) ·d ₀  Equation 7

where u_(c) denotes the unit color vector of the skin reflection and c₀denotes the reflection strength. Substituting (3), (4), (5) and (6) into(1), produces:

C _(k)(t)=I ₀·(1+ψ(m(t),p(t)))(u _(c) ·c ₀ +u _(s)·Φ(m(t),p(t))+(u_(abs) +u _(sub))·p(t))+v _(n)(t)  Equation 8

As the time-varying components are orders of magnitude smaller than thestationary components in equation 7, any product between varying termscan be neglected to approximate

C _(k)(t) as: C _(k)(t)≈u _(c) ·I ₀ ·c ₀ +u _(c) ·I ₀ ·c₀·ψ(m(t),p(t))+u _(s) ·I ₀·Φ(m(t),p(t))+(u _(abs) +u _(sub))·I ₀ ·p(t)+v_(n)(t)  Equation 9

For synthesizing data for physiological measurement methods, it isdesirable to create skin with RGB changes that vary with p(t). Using aprincipled bidirectional scattering distribution function (BSDF) shader,both of the components of u_(p), u_(abs) and u_(sub) can be capturedusing the subsurface color and subsurface radius parameters. Thespecular reflections are controlled by the specular parameter. Thus, fora given pulse signal, p(t), the skin's appearance over time can besynthesized. Furthermore, the skin's appearance together with changes ina wide variety of other variations can be synthesized, which for thepurposes of vital sign measurement represents noise sources. Datasynthesized in this way is very useful for improving thegeneralizability of camera-based vital signal measurement algorithms.

For any of the video-based physiological measurement methods, the taskis to extract p(t) from C_(k) (t). The motivation for using a machinelearning model to capture the relationship between C_(k) (t) and p(t) inequation 8 is that a neural model can capture more complex relationshipsthan hand-crafted demixing or source separation algorithms (e.g., ICA,PCA) that have ignored p(t) inside Φ(·) and ψ(·), and assumed a linearrelationship between C_(k) (t) and p(t).

High-fidelity facial avatars and physiologically based animation models(the basis for which is described above) are generated for simulatingvideos of faces with a realistic blood flow (pulse) signal. These videosare then used to train a neural model for recovering the blood volumepulse (BVP) from video sequences. The resulting model may be tested onreal video benchmark datasets.

To synthesize the physio-realistic appearance of the avatars,photoplethysmographic waveforms recordings may be used. For example,various photoplethysmograms (PPG) and respiration datasets with varyingcontact PPG recordings and sampling frequencies from differentindividuals may be used. The PPG recordings from different subjects maybe used to synthesize multiple avatars. The synthesized video may be ofany length, such as a short sequence (nine 10-second sequences);accordingly, only a small portion of a PPG recording may be used.

A realistic model of facial blood flow is synthesized in order to traina machine learning model. Accordingly, blood flow may be simulated byadjusting properties of the physically based shading material used torender the face of the avatar. That is, the albedo component of thematerial is a texture map transferred from a high-quality 3D face scan.In some instances, the facial hair has been removed from these texturesso that the skin properties can be easily manipulated (3D hair can beadded later in the process). Specular effects are controlled with aroughness map, to make some parts of the face (e.g. the lips) shinierthan others.

As blood flows through the skin, the composition of the skin changes andcauses variations in subsurface color. The skin tone changes may bemanipulated using subsurface color parameters. The weights for thesubsurface color parameters may be derived from the absorption spectrumof hemoglobin and typical frequency bands from digital cameras.Accordingly, the subsurface color parameters may be varied across allskin pixels on an albedo map (but not non-skin pixels). An albedo mapmay be an image texture without any shadows or highlights. Further, thesubsurface radius for the channels to capture the changes in subsurfacescattering as the blood volume varies. The subsurface scattering isspatially weighted using a subsurface scattering radius texture whichcaptures variations in the thickness of the skin across the face. TheBSDF subsurface radii for the RGB channels may be varied using the sameweighting prior as above. Empirically these parameters work forsynthesizing data for training camera-based vital sign measurement.Varying the subsurface scattering alone, without changes in subsurfacecolor, may be too subtle and may not recreate the effects the BVP onreflected light observed in real videos. Alternatively, or in addition,color spaces other than RGB may be used. For example, color spacesincluding luminance and chrominance channels (e.g., YUV, Y′UV, YCrCb,Y′CrCb may be used. Similarly, the hue, saturation, and value (HSV)color space may be used.

By precisely specifying what type of variation appears in the data, amachine learning system may be trained that is robust to that form ofvariation encountered in the real world. A number of differentsystematic variations may be employed with the aspects disclosed hereinsuch as, facial appearance, head motion, facial expression, andenvironment. For example, faces may be synthesized with fifty differentappearances. For each face, the skin material may be configured with analbedo texture picked at random from an albedo collection. In order tomodel wrinkle-scale geometry, a matching high-resolution displacementmap that was transferred from the scan data may be applied. Skin type isparticularly important in imaging PPG measurement; accordingly, anapproximate skin type distribution for the faces may include adistribution that is not uniform but does represent a much more balanceddistribution than in existing imaging PPG datasets. Since motion is oneof the greatest sources of noise in imaging PPG measurement, a set ofrigid head motions may be simulated to augment training examples thatcapture these conditions. In particular, the head may be smoothlyrotated about the vertical axis at angular velocities of 0, 10, 20, and30 degrees/second similar to head motions, facial expressions movementsare also a frequent source of noise in PPG measurement. To simulateexpressions, videos may be synthesized with smiling, eye blinking, andmouth opening (similar to speaking), which are some of the most commonfacial expressions exhibited in everyday life. Smiles and blinks may beapplied to the face using blend shapes, and the mouth may be opened byrotating the jawbone with linear blend skinning. Faces may be renderedin different image-based environments to create a realistic variety inboth background appearance and illumination on the face. Both staticbackgrounds and backgrounds with motion may be used. In some instances,even facial occlusions that more closely resemble challenging real-lifeconditions were included.

FIG. 1 depicts details directed to generating and then usingphysio-realistic synthetic avatars to train a machine learning model fordetection of a physiological signal in accordance with examples of thepresent disclosure. That is, a physio-realistic avatar generator 116 maygenerate synthesized videos of physio-realistic avatars 120; thesynthesized videos of physio-realistic avatars 120 may then be used totrain an end-to-end learning model 136, such as a neural model, forrecovering or identifying a particular physiological response from videosequences. The physio-realistic avatar generator 116 may synthesize thephysio-realistic avatars based on physiological data 104, appearancedata 108, and parameter data 112. The physiological data 104 may includeone or more signals indicative of a physiologic response, condition, orsignal. For example, the physiological data 104 may correspond to bloodvolume pulse measurements based on a real human recording, such as ablood volume pulse waveform. As another example, the physiological data104 may correspond to a respiratory rate/waveform, a heart conditionindicated by a waveform or measurement such as atrial fibrillation,and/or oxygen saturation levels. For example, the physiological data 104may correspond to ballistocardiography (BCG) and/or respiration data andmay be a ballistocardiographic waveform or respiratory waveform. Asanother example, the physiological data 104 may be aphotoplethysmographic waveform. A photoplethysmography waveform may begenerated by an optical sensor to measure blood volume changes in anon-contact manner. Photoplethysmograph provides useful physiologicalinformation to assess the cardiovascular function and PPG signals arecommonly measured by transmission and reflection methods which senselight transmitted through or reflected by tissues. In some examples, thephysiological data 104 may be utilized to assess one or more conditions,such as but not limited to peripheral arterial disease, the Raynaud'sphenomenon and systemic sclerosis, and Takayasu's arteritis. A PPGwaveform also changes with breathing pattern. For example, theamplitude, frequency, and baseline of PPG waveform are modulated byrespiration. The physiological data 104 may include other waveforms,measurements, or otherwise and may be from different individuals. Insome examples, the waveforms may be recordings of various lengths andvarious sample rates.

The appearance data 108 may include skin material with an albedo textureselected from random. In some examples, the albedo component of thematerial is a texture map transferred from a high-quality 3D face scan.As noted above, in some examples, the facial hair has been removed fromthese textures so that the skin properties can be easily manipulated.Specular effects may be controlled to make some parts of the face (e.g.the lips) shinier than others. In some examples, wrinkle-scale geometrymay be applied using a high-resolution displacement map transferred fromscan data. Skin type may also be randomly selected. For example, skintype may be selected from one of the six Fitzpatrick skin types. TheFitzpatrick skin type (or phototype) depends on the amount of melaninpigment in the skin. This is determined by constitutional color (white,brown or black skin) and the result of exposure to ultraviolet radiation(tanning). The Fitzpatrick skin types may include: I. pale white skin;II. fair skin; III. darker white skin; IV light brown skin; V brownskin; and VI. dark brown or black skin. In some examples, skin typeclassifications other than Fitzpatrick skin types may be utilized.

The parameter data 112 may include parameters affecting the avatarand/or light transmission and reflectance. For example, the parameterdata 112 may include facial expressions, head motions, backgroundillumination, environment, etc. Since motion is one of the greatestsources of noise in imaging PPG measurement, rigid head motions may beused to augment training examples that capture such conditions. A headmay be rotated about the vertical axis at varying degrees of angularvelocities, such as 0, 10, 20, and 30 degrees/second. Similarly, tosimulate expressions, videos may be synthesized with smiling, eyeblinking, and mouth opening (similar to speaking), and/or other commonfacial expressions exhibited in everyday life. Smiles and blinks may beapplied to the face using a collection of blend shapes; the mouth may beopened by rotating the jawbone with linear blend skinning. In addition,different environments may be utilized to render the avatars to create arealistic variety of avatars in both background appearance andillumination on the face. In some examples, a video sequence depicting aphysio-realistic avatar may include a static background. Alternatively,or in addition, the background may include motion or avatar occlusionsthat more closely resemble challenging real-life conditions. Theparameter data 112 may also include environmental conditions; forexample, the parameter data 112 may include temperature, time of day,weather such as wind, rain, snow, etc.

The physiological data 104, appearance data 108, and parameter data 112may be provided to the physio-realistic avatar generator 116. Thephysio-realistic avatar generator 116 may use a bidirectional scatteringdistribution function (BSDF) shader to render the physio-realisticavatar and combine the physio-realist avatar with a background. Further,synthesized videos of physio-realistic avatars 120 may be generated. Thesynthesized videos of physio-realistic avatars 120 may include variousvideo sequences depicting different physio-realistic avatars 122 and 124for example. In some examples, the physio-realistic video sequenceand/or physio-realistic avatars may be stored in the physio-realisticavatar video repository 128. One or more of the physio-realistic avatars122 may be tagged as training data 123. An example of a training labelincludes, but is not limited to blood volume pulse and/or peripheralarterial disease. Accordingly, when using the synthesized video to traina machine learning model, the label may identify one or morecharacteristics of the video as training and/or test/validation data.The synthesized videos of physio-realistic avatars 120 may be providedto an end-to-end learning model 136, such as a convolutional attentionnetwork (CAN) to evaluate the impact of synthetic data on the quality ofrecovered physiologic signal 140 from the video sequences. In addition,the end-to-end learning model 136 may be trained with the synthesizedvideos of physio-realistic avatars 120 in addition to real human videos132.

The CAN uses motion and appearance representations learned jointlythrough an attention mechanism. The approach mainly consists of atwo-branch convolutional neural network, the motion branch allows thenetwork to differentiate between intensity variations caused by noise,e.g., from motion from subtle characteristic intensity variationsinduced by physiological characteristic, such as blood flow. The motionrepresentation is the difference of two consecutive video frames. Toreduce the noise from changes in ambient illumination and the distanceof the face to the illumination source, the frame difference is firstnormalized based on the skin reflection model. The normalization isapplied to a video sequence by subtracting the pixel mean and dividingby the standard deviation. The appearance representation captures theregions in the image that contribute strong iPPG signals. Via theattention mechanism, the appearance representation guides the motionrepresentation and helps differentiate the iPPG signal from the othersources of noise. The input frames are similarly normalized bysubtracting the mean and dividing by the standard deviation.

Once trained with physio-realistic avatars and/or the real human videos132, the end-to-end learning model 136 may be used to evaluate videoinformation of a subject 148. The subject 148 may be instrumented suchthat a physiological signal provided by a gold standard, contact and/ornon-contact measurement device or sensor can be compared to therecovered physiologic signal 152 for the same participant. Accordingly,the two physiological signals may be compared to one another todetermine an effectiveness of the end-to-end learning model 136. Uponfinding that the end-to-end learning model 136 is effective and/or ofdesired accuracy, the trained model, including the model structure andmodel weights, may be stored in the physiological model repository 156such that the trained model may be used to recover a physiologicalsignal of different participants or subjects.

FIG. 2 depicts additional details directed to synthesizing video framesincluding physio-realistic avatars in accordance with examples of thepresent disclosure. More specifically, an albedo 204 may be selected;the selection section of the albedo 204 may correspond to a texture maptransferred from a high-quality 3D face scan. The albedo may be chosenat random or chosen to represent a specific population. The albedo maybe devoid of facial hair so that the skin properties can be easilymanipulated. Other parameters affecting appearance, such as but notlimited to skin color/type, hair, specular effects, wrinkles, etc., maybe added via appearance parameters 208. Skin type may be randomlyselected or selected to represent a specific population. For example,skin type may be selected from one of the six Fitzpatrick skin types,however one of skill in the art will appreciate that classificationsother than Fitzpatrick skin types may be utilized.

As blood flows through the skin, the composition of the skin changes andcauses variations in subsurface color. Accordingly, skin tone changesmay be manipulated using the subsurface color parameters including, butnot limited to, the base sub-surface skin color 212, the sub-surfaceskin color weights 220, and sub-surface skin scattering parameters 228.The weights for the sub-surface skin color weights 220 may be derivedfrom the absorption spectrum of hemoglobin and typical frequency bandsfrom example digital cameras. For example, an example camera may providecolor based on the following frequency bands: red: 550-700 nm; green:400-650 nm; and blue: 350-550 nm. The sub-surface skin color weights 220may include a weight for one or more of the color channels and may beapplied to the physiological data 216, where the physiological data 216may be same as or similar to the physiological data 104 previouslydescribed and may include one or more signals indicative of aphysiologic response, condition, or signal. For example, thephysiological data 216 may correspond to blood volume pulse measurementsbased on a real human recording, such as a blood volume pulse waveform.As another example, the physiological data 216 may correspond to arespiratory rate/waveform, a heart condition indicated by a waveform ormeasurement such as atrial fibrillation, and/or oxygen saturationlevels. For example, the physiological data 216 may correspond toballistocardiography (BCG) and may be a ballistocardiographic waveform.As another example, the physiological data 216 may be aphotoplethysmographic waveform. In some examples, the physiological data216 may be based on signal measurement from an actual human or may besynthesized based on known physiological signal characteristicsindicative of a physiological response, condition, or signal. Theweighted physiological data signal resulting from the application of thesub-surface skin color weights 220 may be added to the base sub-surfaceskin color 212 resulting in the sub-surface skin color 224 comprisingmultiple color channels. The sub-surface skin color 224 may be providedto the shader 232. In some examples, the sub-surface skin color weights220 may be applied to all pixels determined to be facial pixels on thealbedo map; the sub-surface skin color weights 220 may not be applied tonon-skin pixels.

In addition, the subsurface radius may be manipulated for the colorchannels to capture the changes in subsurface scattering as thephysiological characteristic, such as blood volume, varies. Thesubsurface scattering is spatially weighted using a subsurfacescattering radius texture which captures variations in the thickness ofthe skin across the face. The subsurface radii for the RGB channels maybe varied using weights that are the same or similar to the sub-surfaceskin color weights 220.

In some examples, external parameters 210 may alter a skin tone andcolor. The external parameters 210 may include parameters affecting theavatar and/or light transmission and reflectance. For example, theexternal parameters 210 may include facial expressions, head motions,background illumination, environment, etc. Since motion is one of thegreatest sources of noise in imaging PPG measurement, rigid head motionsmay be used to augment training examples that capture such conditions. Ahead may be rotated about the vertical axis at varying degrees ofangular velocities, such as 0, 10, 20, and 30 degrees/second. Similarly,to simulate expressions, videos may be synthesized with smiling, eyeblinking, and mouth opening (like speaking), and/or other common facialexpressions exhibited in everyday life. Smiles and blinks may be appliedto the face using a collection of blend shapes; the mouth may be openedby rotating the jawbone with linear blend skinning.

In some examples, the physiological processes that are modeled causeboth color and motion changes; accordingly, motion weights 222 may beapplied to the physiological data 216 to account for pixel movement andpixel translation caused, at least in part by, the physiological data216. For example, a region, portion, or area represented by one or morepixels, may move from a first location in a first frame to a secondlocation in a second frame. Accordingly, the motion weights may providea mechanism for identifying and/or addressing specific pixels of theinput image that move or translate due, at least in part to, thephysiological characteristic. As an example, blood flowing through avein, artery, and/or under the skin may cause the vein, artery, and/orskin to distort in one or more directions. The motion weights 222 mayaccount for such movement or translation, and in some instances may berepresented as a vector.

In examples, the shader 232 may provide an initial rendering of one ormore pixels of the avatar based on the external parameters 210, theappearance parameters 208, the sub-surface skin color 224, thesub-surface skin scattering parameters 228, the motion weights, and thephysiological data 216. Of course, other parameters may be considered aswell. The shader 232 may be a program that runs in a graphics pipelineproviding instructions to a computer processing unit, such as a graphicsprocessing unit, that indicate how to render one or more pixels. Inexamples, the shader 232 may be a principled bidirectional scatteringdistribution function (BSDF) shader, that determines the probabilitythat a specific ray of light will be reflected (scattered) at a givenangle.

The image rendered by the shader 232 may be an avatar for a specificframe of video. In some examples, a background 236 may be added to theavatar such that the avatar appears in front of an image. In someexamples, the background 236 may be static; in some examples, thebackground 236 may be dynamic. And further, in some examples, aforeground object included with the background 236 may occlude a portionof the avatar. The sequence of frames 240 may be synthesized at 240 suchthat a video sequence is obtained. Such frames may be assembled with avideo synthesizer configured to apply backgrounds and/or assemble aplurality of frames or images into a video sequence. In some examples,the background 236 may be rendered together with the avatar by theshader 232.

FIG. 3 depicts additional details of the directed to a physio-realisticvideo generator 304 configured to render and synthesize physio-realisticvideo sequences including physio-realistic avatars in accordance withexamples of the present disclosure. The physio-realistic video generator304 may be a computing device and/or specialized computing devicespecifically configured to render and synthesize video. Thephysio-realistic video generator 304 may include multiple devices and/orutilize a portion of a cloud infrastructure to divide one or moreportions of the rendering and/or synthesizing tasks among differentdevices. The physio-realistic video generator 304 may include aphysio-realistic shader 308 and a frame synthesizer 312.

The physio-realistic shader 308 may be the same as or similar to theshader 232 and may provide an initial rendering of one or more pixels ofan avatar based on the appearance parameters 320, the albedo 324, thephysiological data 328, the sub-surface skin parameters 332, thebackground 336, and the external parameters 340. Of course, otherparameters may be considered by the physio-realistic shader 308 as well.The appearance parameters 320 may be the same as or similar to theappearance parameters 208; the albedo 324 may be the same as or similarto the albedo 204; the physiological data 328 may be the same as orsimilar to the physiological data 216; the sub-surface skin parameters332 may be the same as or similar to the base sub-surface skin color212, the sub-surface skin color weights 220, the sub-surface skinscattering parameters 228; the background 336 may be the same as orsimilar to the background 236, and the external parameters 340 may bethe same as or similar to the external parameters 210.

The image rendered by the physio-realistic shader 308 may be an avatarexhibiting a specific physiological response based on the physiologicaldata 328 and may be rendered to a frame of video as previouslydiscussed. In some examples, the avatar may be rendered in front of abackground 336 such that the avatar appears in front of an image. Insome examples, the background 336 may be static; in some examples, thebackground 336 may be dynamic. And further, in some examples, aforeground object included in the background 336 may occlude a portionof the avatar. The frames generated by the physio-realistic shader 308may be provided to the frame synthesizer 312 for synthesizing and forassembling the frames into a video sequence. The synthesized video maythen be provided to the physio-realistic avatar video repository 316which may be the same as or like the physio-realistic avatar videorepository 128.

The synthesized video may be tagged or labeled prior to being stored;alternatively, or in addition, the synthesized video may be stored in alocation or repository associated with a specific label. An example of alabel includes, but is not limited to blood volume pulse and/orperipheral arterial disease. Accordingly, when using the synthesizedvideo to train a machine learning model, the label may identify one ormore characteristics of the video as training and/or test/validationdata.

FIG. 4 depicts additional details directed to training a machinelearning structure 404 to build a machine learning model 442 based ontraining data 408 including synthesized physio-realistic videos from asynthesized video repository 412 and human videos from a human videorepository 416 in accordance with examples of the present disclosure.The synthesized physio-realistic videos may be output from the framesynthesizer 312 as previously described and may be labeled with atraining label to identify one or more physiological characteristics. Anexample of a training label includes, but is not limited to blood volumepulse and/or peripheral arterial disease. The human videos are videos ofreal individuals. In some examples, the machine learning structure 404utilizes training data that includes synthesized physio-realisticvideos, human videos, or a combination of the two. The machine learningstructure 404 may be stored in a file as processor executableinstructions such that when a collection of algorithms associated withthe machine learning structure 404 are executed by a processor, amachine learning model 442 including various layers and optimizationfunctions and weights is constructed. That is, the various layerscomprising the architecture of the machine learning structure 404 mayiteratively train utilizing the training data 408 to recover aphysiological signal 440 present in the training data 408. The variouslayers comprising the machine learning structure 404 may be trained toidentify and obtain the physiological signal 440. After many iterations,or epochs, the configuration of the machine learning structure 404(e.g., the various layers and weights associated with one or morelayers) having the least amount of error associated with an iterationmay be utilized as the machine learning model 442, where the structureof the machine learning model may be stored in the model file 444 andthe weights associated with one or more layers and/or configurations maybe stored in the model weights file 448.

In accordance with examples of the present disclosure, the machinelearning structure 404 may include two paths; a first path associatedwith a motion model 424 and a second path associated with an appearancemodel 432. The architecture of the motion model 424 may include ninelayers with 128 hidden units for example. In addition, an averagepooling and hyperbolic tangent may be utilized as the activationfunctions. The last layer of the motion model 424 may include linearactivation units and a mean squared error (MSE) loss. The architectureof the appearance model 432 may be the same as the motion model 424 butwithout the last three layers (e.g., Layer 7, Layer 8, and Layer 9).

The motion model 424 allows the machine learning structure 404 todifferentiate between intensity variations caused by noise, e.g., frommotion from subtle characteristic intensity variations induced by thephysiological characteristic. The motion representation is computed fromthe input difference of two consecutive video frames 420 (e.g., C(t) andC(t+1). The ambient illumination may not be uniform on the face and theillumination distribution changes with the distance of the face to thelight source and may be affecting the supervised learning approach.Therefore, to reduce these sources of illumination noise, the framedifference is first normalized at 428 using an AC/DC normalization basedon the skin reflection model. The normalization may be applied once tothe entire video sequence by subtracting the pixel mean and dividing bythe standard deviation. In addition, one or more of the layers, Layer1-Layer 5, may be a convolution layer of different or the same size andmay be utilized to identify various feature maps utilized through thetraining of the machine learning structure 404. In examples, thenormalization difference 428 may correspond to a normalized differencefor three color channels, such as a red, green, and/or blue colorchannel. The various layers of the motion model 424 may include featuremaps and/or various convolutions of various sizes and color channels.

The appearance model 432 allows the machine learning structure 404 tolearn which regions in the image are likely to be reliable for computingstrong physiological signals, such as iPPG signals. The appearance model432 may generate a representation from an input video frame's textureand color information. The appearance model 432 guides the motionrepresentation to recover iPPG signals from various regions included inthe input image, and to further differentiate between them from othersources of noise. The appearance model 432 may take as input a singleimage or frame of video. That is, a single frame of video or image 436may be utilized as an input to the various layers, Layers 1-Layers 6).

Once trained, the machine learning structure 404 may be output as amachine learning model 442 where the structure of the machine learningstructure 404 may be stored in the model file 444 and the variousweights of the machine learning model are stored in the model weightsfile 448. Although depicted with a specific deep learningimplementation, it should be understood that the machine learningstructure may be modified, tuned, or otherwise changed to achieve agreatest amount of accuracy associated with detecting a physiologicalsignal, such as blood volume pulse.

FIG. 5 depicts an example of how an input physiological signal 504, suchas a pulse signal, is rendered to the physio-realistic avatar andinfluences the RGB pixel values in the resulting video frames 508. Forexample, an input physiological signal 504 may correspond to a bloodvolume flow based on a real human recording; the input physiologicalsignal 504 may be a blood volume pulse waveform. As another example, thephysiological signal 504 may correspond to a respiratory rate/waveform,a heart condition indicated by a waveform or measurement such as atrialfibrillation, and/or oxygen saturation levels. For example, thephysiological signal 504 may correspond to ballistocardiography (BCG)data and may be a ballistocardiographic waveform. As another example,the physiological signal 504 may be a photoplethysmographic waveform.The physiological signal 504 may include other waveforms, measurements,or otherwise and may be from different individuals. In some examples,the waveforms may be recordings of various lengths and various samplerates.

As depicted in FIG. 5 , an avatar 506 exhibiting the physiologicalsignal 504 may be generated in multiple video frames 508 of a videosequence as previously described. A scanline 510 of the avatar 506 isdepicted over time in 512. The corresponding RGB pixels (red 520, blue524, and green 528) are depicted over time in the graph 516. As shown inthe graph 516, a detrended waveform corresponding to a pulse signal canbe identified from the RGB pixels. Alternatively, or in addition, colorspaces other than RGB may be used. For example, color spaces includingluminance and chrominance channels (e.g., YUV, Y′UV, YCrCb, Y′CrCb maybe used. Similarly, the hue, saturation, and value (HSV) color space maybe used.

FIG. 6 depicts additional details of a system 600 for using a trainedmachine learning model to recover a physiological signal from a videosequence in accordance with examples of the present disclosure. Thesystem 600 may include a subject, or patient 604 within a field-of-viewof a camera 608. The subject 604, or patient, may be a real human andmay or may not exhibit one or more physiological characteristics. Forexample, the system 600 may utilize a trained machine learning model,such as the machine learning model 620, to recover, or determine, one ormore physiological characteristics of the subject 604. The physiologicalcharacteristics may be a pulse rate and/or an assessment of acardiovascular function. As non-limiting examples, peripheral arterialdisease, the Raynaud's phenomenon and systemic sclerosisa, andTakayasu's arteritis may be assessed. While examples provided herein aresubstantially directed to cardiovascular functions, other physiologicalcharacteristics and/or conditions are contemplated.

The camera 608 may correspond to any camera capable of capturing ortaking a plurality of images. In some examples, the camera 608 maycapture a sequence of frames 612, or images, at a specific frame rate.An example frame rate may include but is not limited to 32 frames persecond or 16 frames per second. Of course, other frame rates arecontemplated herein. The camera may provide the video including thesequence of frames 612 to a physiological measurement device 616. Thephysiological measurement device 616 may be a computing device or otherdevice capable of executing the machine learning model 620. In someexamples, the physiological measurement device 616 may be distributedamongst several computing devices and/or may utilize a cloudinfrastructure. In some examples, the physiological measurement device616 may comprise a service, such as a web service that receives asequence of frames and provides a recovered physiological signal, suchas a heart rate.

The physiological measurement device 616 may execute the machinelearning model 620 to process the sequence of frames 612. In examples,the machine learning model 620 may utilize the model/structure data 624to create, or generate, a model structure. The model structure may bethe same as or similar to the machine learning structure that wastrained with one or more video sequences. For example, themodel/structure data 624, upon being executed, or ran by thephysiological measurement device 616, may generate a model structurethat is similar to the machine learning structure of FIG. 4 . The modelweights data 628 may be utilized to weight one or more portions, orfeatures, of the newly created model structure as determined during themachine learning process. Accordingly, the machine learning model 620may receive the sequence of frames 612 and process the frames torecover, or identify, a physiological signal 632. The physiologicalmeasurement device 616 may further process the recovered physiologicalsignal 632 to output, or provide, a physiological measurement orassessment 636. The physiological measurement may be a rate, such as apulse rate for example. In some examples, the physiological assessmentmay correspond to a measure of similarity to a predicted training label,such as a condition. In some examples, the physiological measurement orassessment 636 may be stored in a repository or provided to the subject604 or caregivers of the subject 604.

FIG. 7 depicts examples of a recovered waveform corresponding to a pulsefrom machine learning model, such as the machine learning model 620 inaccordance with examples of the present disclosure. One or morephysiological signals may be recovered, for example, from the machinelearning model 620 as a recovered physiological signal 632. Examplerecovered physiological signals may include signals depicted in FIG. 7 .That is, a machine learning model, such as the machine learning model620 may be trained using only real human videos; the machine learningmodel 620 may recover a waveform, such as the waveform 704, where apower spectrum analyses indicates that a dominant frequency occurs at 92beats per minute (BPM) as illustrated in graph 708. Such a recoveredwaveform and pulse generally agree with one or more readings of acontact sensor as depicted by the waveform 720 and resulting pulse showin the graph 724. Further, a machine learning model, such as the machinelearning model 620 may be trained using both the physio-realistic avatarvideos, such as those depicted as 122 and 124 in FIG. 1 , together withreal human videos such as those videos depicted in FIG. 1 . The machinelearning model 620 may recover a waveform, such as the waveform 712,where a power spectrum analyses indicates that a dominant frequencyoccurs at 92 beats per minute (BPM) as shown by graph 716. Such arecovered waveform and pulse generally agree with one or more readingsof a contact sensor as depicted by the waveform 720 and resulting pulseshown in graph 724.

As another example, a machine learning model, such as the machinelearning model 620 may be trained using only real human videos; themachine learning model 620 may recover a waveform, such as the waveform728, where a power spectrum analyses indicates that a dominant frequencyoccurs at 69 beats per minute (BPM) as illustrated in the graph 732.Such a recovered waveform and pulse do not agree with one or morereadings of a contact sensor as depicted by the waveform 736 andresulting pulse shown in the graph 740. Further, a machine learningmodel, such as the machine learning model 620 may be trained using boththe physio-realistic avatar videos, such as those depicted as 122 and124 in FIG. 1 , together with real human videos such as those videosdepicted in FIG. 1 . The machine learning model 620 may recover awaveform, such as the waveform 736, where a power spectrum analysesindicates that a dominant frequency occurs at 92 beats per minute (BPM)as shown by graph 740. Such a recovered waveform and pulse generallyagree with one or more readings of a contact sensor as depicted by thewaveform 744 and resulting pulse shown in graph 748. Accordingly, byusing real and physio-realistic synthesized videos, the recoveredphysiological signal may be more accurate or otherwise correspond tobetter to a non-contact, gold standard, measurement.

FIG. 8 depicts a system 800 including details of a physio-realisticvideo generator and/or a generator for a machine learning model trainedwith synthesized physio-realistic video in accordance with examples ofthe present disclosure. That is, a device, such as a computing device804, may interact with a physio-realistic video/model generator 824 toretrieve and/or have generated in real-time or substantially real-time,one or more of a synthesized physio-realistic video sequences and/or aphysiological model. For example, a user operating a computing device804 may desire training data to train their own machine learning modelto recover a physiological signal. In some examples, a user operatingthe computing device 804 may desire to obtain a machine learning modelfor integration into a physiological measurement system. As anotherexample, a user operating the computing device 804 may desire to haveexisting physiological data, such as a physiological waveform,anonymized such that an avatar exhibits the physiological characteristicinstead of an actual human. In some example, a user operating thecomputing device 804 may wish to have an avatar exhibiting aphysiological characteristic generated for a specific cinematic effect.Accordingly, the user may utilize the physio-realistic video/modelgenerator 824 to obtain such synthesized physio-realistic videosequences and/or models.

The user, via the computing device 804, may browse one or more of thephysio-realistic avatar video repositories 816 and/or the physiologicalmodel repository 812 for synthesized physio-realistic video sequencesand/or models. If, for example, a user is unable to locate a desiredsynthesized physio-realistic video sequence and/or model, the user mayselect one or more parameters via a user interface 820. The one or moreparameters may include, but are not limited to, appearance parameters828, an albedo 832, a physio-realistic data signal 836, subsurface skinparameters 840, a background 844, and/or other external parameters 848as previously described with respect to FIG. 3 . The user may submitsuch parameters using as submit feature or button 852 such that theparameters are provided to the physio-realistic video/model generator824 via the network 808. The physio-realistic video/model generator 824may proceed to generate synthesized physio-realistic video sequences ina manner consistent with FIGS. 1-3 utilizing the physiological shader858 and the frame synthesizer 862 of a physio-realistic video generator856. In some examples, the physio-realistic video/model generator 824may proceed to generate one or more physiological models utilizing amachine learning model 860. The physio-realistic video/model generator824 may then provide the synthesized physio-realistic video sequencesand/or the physiological models to either one or more of therepositories 812 or 816 and/or to the user operating the computingdevice 804 as synthesized physio-realistic video sequences 868 and/orphysiological model 872.

In some examples, a user operating the computing device 804 may providephysiological data 864 such that synthesized physio-realistic videosequences based on the physiological data 864 are generated. Forexample, the physiological data 864 may be obtained using a goldstandard, contact and/or non-contact measurement device or sensor, ormay be a recovered physiologic signal, such as the recovered physiologicsignal 140. The physio-realistic video/model generator 824 may generatesynthesized physio-realistic video sequences based on the physiologicaldata 864 and provide the synthesized physio-realistic video sequences868 to the user via the network 808.

FIG. 9 depicts details of a method 900 for generating physio-realisticavatar videos in accordance with examples of the present disclosure. Ageneral order for the steps of the method 900 is shown in FIG. 9 .Generally, the method 900 starts at 904 and ends at 932. The method 900may include more or fewer steps or may arrange the order of the stepsdifferently than those shown in FIG. 9 . The method 900 can be executedas a set of computer-executable instructions executed by a computersystem and encoded or stored on a computer readable medium. Further, themethod 900 can be performed by gates or circuits associated with aprocessor, Application Specific Integrated Circuit (ASIC), a fieldprogrammable gate array (FPGA), a system on chip (SOC), or otherhardware device. Hereinafter, the method 900 shall be explained withreference to the systems, components, modules, software, datastructures, user interfaces, etc. described in conjunction with FIGS.1-8 .

The method starts at 904, where flow may proceed to 908. At 908,physiological data may be received. The physiological data may includeone or more signals indicative of a physiologic response, condition, orsignal. For example, the physiological data may correspond to bloodvolume pulse measurements based on a real human recording, such as ablood volume pulse waveform. As another example, the physiological datamay correspond to a respiratory rate/waveform, a heart conditionindicated by a waveform or measurement such as atrial fibrillation,and/or oxygen saturation levels. For example, the physiological data maycorrespond to ballistocardiography (BCG) and may be aballistocardiographic waveform. As another example, the physiologicaldata may be a photoplethysmographic waveform. In some examples, thephysiological data may be utilized to assess one or more conditions,such as but not limited to peripheral arterial disease, the Raynaud'sphenomenon and systemic sclerosis, and Takayasu's arteritis. Thephysiologic data may include other waveforms, measurements, or otherwiseand may be from different individuals. In some examples, the waveformsmay be recordings of various lengths and various sample rates.

The method 900 may proceed to 912, where the received physiological datais adjusted or otherwise modified by the sub-surface skin color weights.As blood flows through the skin, the composition of the skin changes andcauses variations in subsurface color. Accordingly, skin tone changesmay be manipulated using the subsurface color parameters including, butnot limited to, the base sub-surface skin color, the sub-surface skincolor weights, and sub-surface skin scattering parameters. The weightsfor the sub-surface skin color weights may be derived from theabsorption spectrum of hemoglobin and typical frequency bands fromexample digital cameras. The sub-surface skin color weights may includea weight for one or more color channels and may be applied to thephysiological data signal.

The method may proceed to 916, where a base sub-surface skin colorforming a base color under the skin may be modified based on theweighted physiological data to obtain a sub-surface skin color. At 920,an albedo may be selected. The albedo may correspond to a texture maptransferred from a high-quality 3D face scan. The albedo may be chosenat random or chosen to represent a specific population. The albedo maybe devoid of facial hair so that the skin properties can be easilymanipulated. Skin type may be randomly selected or selected to representa specific population. For example, skin type may be selected from oneof the six Fitzpatrick skin types. The Fitzpatrick skin type (orphototype) depends on the amount of melanin pigment in the skin. At 922,the method 900 may generate, or otherwise account for, motion changesdue at least in part to, the physiological data. In some examples, thephysiological processes that are modeled cause both color and motionchanges; accordingly, motion weights, such as the motion weights 222,may be applied to the physiological data to account for pixel movementand pixel translation caused, at least in part by, the physiologicaldata. The method 900 may then proceed to 924, where a physio-realisticavatar may be rendered based on the albedo and the sub-surface skincolor. In some examples, additional parameters, such as appearanceparameters, other sub-surface skin parameters, the motion weights, andexternal parameters as previously discussed may affect the rendering ofthe avatar. In some examples, the avatar may be rendered by aphysio-realistic shader, such as the physio-realistic shader 308previously described. As the physiological signal received at 908 may betemporal, multiple images of the avatar, shifted in time, may berendered.

The method 900 may proceed to 928, where the multiple images of theavatar shifted in time may be synthesized together to form aphysio-realistic avatar video of a predetermined length. In someexamples, a static or dynamic background may be synthesized togetherwith the rendered avatar. The method 900 may then proceed to 932, wherethe physio-realistic avatar video may be stored in a physio-realisticavatar video repository, such as the physio-realistic avatar videorepository 316 previously described. The physio-realistic avatar videomay be tagged or labeled with a training label prior to being stored;alternatively, or in addition, the physio-realistic avatar may be storedin a location or repository associated with a specific training label.An example of a training label includes, but is not limited to bloodvolume pulse and/or peripheral arterial disease. Accordingly, when usingthe physio-realistic avatar video to train a machine learning model, thetraining label may identify one or more characteristics of the video astraining and/or test/validation data. The method 900 may then end at936.

FIG. 10 depicts details of a method 1000 for training a machine learningstructure in accordance with examples of the present disclosure. Ageneral order for the steps of the method 1000 is shown in FIG. 10 .Generally, the method 1000 starts at 1004 and ends at 1020. The method1000 may include more or fewer steps or may arrange the order of thesteps differently than those shown in FIG. 10 . The method 1000 can beexecuted as a set of computer-executable instructions executed by acomputer system and encoded or stored on a computer readable medium.Further, the method 1000 can be performed by gates or circuitsassociated with a processor, Application Specific Integrated Circuit(ASIC), a field programmable gate array (FPGA), a system on chip (SOC),or other hardware device. Hereinafter, the method 1000 shall beexplained with reference to the systems, components, modules, software,data structures, user interfaces, etc. described in conjunction withFIGS. 1-9 .

The method starts at 1004, where flow may proceed to 1008. At 1008,training data may be received. The training data received at 1008 mayinclude physio-realistic avatar videos; in some examples, thephysio-realistic avatar videos may have been synthesized according tothe method 1000 previously discussed. At 1012, one or more videosincluding human participants may be received. That is, a machinelearning structure may benefit from utilizing training data includingboth physio-realistic avatar videos and videos of actual humanparticipants. At 1016, the machine learning structure may be trainedwith both types of videos.

For example, the machine learning structure may include two paths asdiscussed with respect to FIG. 4 . A first path may be associated with amotion model and a second path associated with an appearance model. Thearchitecture of the motion model may include various layers and hiddenunits and may include an average pooling and hyperbolic tangent that maybe utilized as an activation function. The architecture of theappearance model may be the same as or similar to the motion model. Themotion model allows the machine learning structure to differentiatebetween intensity variations caused by noise, e.g., from motion fromsubtle characteristic intensity variations induced by the physiologicalcharacteristic. The motion representation is computed from the inputdifference of two consecutive video frames (e.g., C(t) and C(t+1). Theappearance model allows the machine learning structure to learn whichregions in the image are likely to be reliable for computing strongphysiological signals, such as iPPG signals. The appearance model maygenerate a representation from one or more of the input video frame'stexture and color information. The appearance model guides the motionrepresentation to recover iPPG signals from various regions included inthe input image, and to further differentiate between them from othersources of noise. The appearance model may take as input a single imageor frame of video.

As part of the training process, the recovered physiological signal maybe compared to a known, or valid physiological signal. Once asatisfactory accuracy is achieved, the machine learning structure may beoutput as a machine learning model at 1020, where the structure of themachine learning model may be stored in the model file and the variousweights of the machine learning model are stored in a locationassociated with a weight file. Once the model has been generated, themethod 1000 may end at 1024.

FIG. 11 depicts details of a method 1100 for identifying and/orgenerating a physio-realistic avatar video to a requestor in accordancewith examples of the present disclosure. A general order for the stepsof the method 1100 is shown in FIG. 11 . Generally, the method 1100starts at 1104 and ends at 1132. The method 1100 may include more orfewer steps or may arrange the order of the steps differently than thoseshown in FIG. 11 . The method 1100 can be executed as a set ofcomputer-executable instructions executed by a computer system andencoded or stored on a computer readable medium. Further, the method1100 can be performed by gates or circuits associated with a processor,Application Specific Integrated Circuit (ASIC), a field programmablegate array (FPGA), a system on chip (SOC), or other hardware device.Hereinafter, the method 1100 shall be explained with reference to thesystems, components, modules, software, data structures, userinterfaces, etc. described in conjunction with FIGS. 1-10 .

The method starts at 1104, where flow may proceed to 1108. At 1108, aselection of one or more physiological characteristics may be received.For example, a user may interact with a user interface, such as the userinterface 820, to select physiological characteristics that are to beembodied by a physio-realistic avatar. Such characteristics may includea condition, trait, or signal that the avatar is to exhibit. As anotherexample, the physiological characteristics may be a pulse rate forexample or an avatar with atrial fibrillation for example. At 1112, auser may interact with the user interface 820 to selection one or moreparameters. For example, the parameters may include but are not limitedto appearance parameters 828, an albedo 832, a physio-realistic datasignal 836, subsurface skin parameters 840, a background 744, and/orother external parameters 848 as previously described with respect toFIG. 3 and FIG. 8 . At 1116, the physiological data may be received. Inexamples, the physiological data received at 1116 may be received from aphysiological data repository. For example, if a user were to desirethat the avatar exhibit a pulse rate of 120 beats per minute,physiological data corresponding to the pulse rate may be obtained froma repository. In some examples, a user may upload physiological data at1116. That is, a user operating a computing device may providephysiological data such that synthesized physio-realistic videosequences are based on the physiological data.

The method 1100 may then move to 1120 where a physio-realistic avatarvideo segment based on the one or more physiological characteristics andone or more physiological parameters may be generated. That is, thephysio-realistic avatar may be generated, or rendered in real-time suchthat the physiological characteristics, parameters, and physiologicaldata are specific to the rendered avatar. In some examples, thephysiological characteristics cause both color and motion changes;accordingly, motion weights, may be applied to the physiological data toaccount for pixel movement and pixel translation caused, at least inpart by, the physiological data. Multiple images of the avatar may begenerated such that the images can be synthesized, together with abackground, into a physio-realistic avatar video. At 1124, thephysio-realistic avatar video may be stored in a physio-realistic avatarvideo repository, such as the physio-realistic avatar video repository128. Portions 1116, 1120, and 1124 of the method 1100 may be optional inthat rather than generating an physio-realistic avatar video based onone or more characteristics, parameters, and physiological data, anexisting physio-realistic avatar video meeting the criteria specified bythe user may be located and provided to the requestor. Accordingly, at1128, the method 1100 may provide the requestor with the requestedvideo, either a real-time video as previously discussed, or apreexisting video. The method 1100 may end at 1132.

FIG. 12 depicts details of a method 1200 for recovering a physiologicalsignal from a video using a machine learning model trained on syntheticphysio-realistic avatars in accordance with examples of the presentdisclosure. A general order for the steps of the method 1200 is shown inFIG. 12 . Generally, the method 1200 starts at 1204 and ends at 1232.The method 1200 may include more or fewer steps or may arrange the orderof the steps differently than those shown in FIG. 12 . The method 1200can be executed as a set of computer-executable instructions executed bya computer system and encoded or stored on a computer readable medium.Further, the method 1200 can be performed by gates or circuitsassociated with a processor, Application Specific Integrated Circuit(ASIC), a field programmable gate array (FPGA), a system on chip (SOC),or other hardware device. Hereinafter, the method 1200 shall beexplained with reference to the systems, components, modules, software,data structures, user interfaces, etc. described in conjunction withFIGS. 1-11 .

The method starts at 1204, where flow may proceed to 1208. At 1208, aplurality of images may be received. The plurality of images maycorrespond to one or more frames of video including a human subject; insome examples, the plurality of images are video segments depicting ahuman subject. The subject, or patient, may be a real human and may ormay not exhibit one or more physiological characteristics. A camera maybe used to capture the plurality of images. The plurality of images maybe provided to the physiological measurement device at 1212. Thephysiological measurement device may be a computing device or a service,such as a web service, that receives the plurality of images and obtainsor identifies a physiological signal, such as a heart rate. Thephysiological measurement device may execute a machine learning model toprocess the plurality of images at 1216. In examples, the machinelearning model may utilize the model/structure data to create, orgenerate, a model structure. The model structure may be the same as orsimilar to the machine learning structure that was trained with one ormore video sequences. For example, the model/structure data, upon beingexecuted, or ran by the physiological measurement device, may generate amodel structure that is similar to the machine learning structure ofFIG. 4 . Model weights data may be utilized to weight one or moreportions, or features, of the newly created model structure asdetermined during the machine learning process. Accordingly, the machinelearning model may receive the plurality of images and process theimages recover, or identify, a physiological signal at 1220.

Once a physiological signal has been recovered, the physiologicalmeasurement device may further process the recovered physiologicalsignal to output, or provide, a physiological measurement or assessmentat 1224. The physiological measurement may be a rate, such as a pulserate for example. In some examples, the physiological assessment maycorrespond to a measure of similarity to a predicted label, such as acondition. In some examples, the physiological measurement or assessmentmay be output at 1228 and stored in a repository or provided to thesubject or caregivers of the subject.

FIGS. 13-15 and the associated descriptions provide a discussion of avariety of operating environments in which aspects of the disclosure maybe practiced. However, the devices and systems illustrated and discussedwith respect to FIGS. 13-15 are for purposes of example and illustrationand are not limiting of a vast number of computing device configurationsthat may be utilized for practicing aspects of the disclosure, describedherein.

FIG. 13 is a block diagram illustrating physical components (e.g.,hardware) of a computing device 1300 with which aspects of thedisclosure may be practiced. The computing device components describedbelow may be suitable for the computing devices described above. In abasic configuration, the computing device 1300 may include at least oneprocessing unit 1302 and a system memory 1304. Depending on theconfiguration and type of computing device, the system memory 1304 maycomprise, but is not limited to, volatile storage (e.g., random accessmemory), non-volatile storage (e.g., read-only memory), flash memory, orany combination of such memories.

The system memory 1304 may include an operating system 1305 and one ormore program modules 1306 suitable for running software applications1307, such as but not limited to a machine learning model 1324, amachine learning structure 1326, and a physio-realistic avatar videogenerator 1325. The machine learning model 1324 may be the same as orsimilar to the machine learning models 144 and 442 as described withrespect to, but not limited to, at least FIGS. 1-12 of the presentdisclosure. The physio-realistic avatar video generator 1325 may be thesame as or similar to the physio-realistic video generator 304 withrespect to, but not limited to, at least FIGS. 1-12 of the presentdisclosure. The machine learning structure 1326 may be the same as orsimilar to the end-to-end learning model 136 and 404 as described withrespect to, but not limited to, at least FIGS. 1-12 of the presentdisclosure. The operating system 1305, for example, may be suitable forcontrolling the operation of the computing device 1300.

Furthermore, embodiments of the disclosure may be practiced inconjunction with a graphics library, other operating systems, or anyother application program and is not limited to any application orsystem. This basic configuration is illustrated in FIG. 13 by thosecomponents within a dashed line 1308. The computing device 1300 may haveadditional features or functionality. For example, the computing device1300 may also include additional data storage devices (removable and/ornon-removable) such as, for example, magnetic disks, optical disks, ortape. Such additional storage is illustrated in FIG. 13 by a removablestorage device 809 and a non-removable storage device 1310.

As stated above, several program modules and data files may be stored inthe system memory 1304. While executing on the at least one processingunit 1302, the program modules 1306 may perform processes including, butnot limited to, one or more aspects, as described herein. Other programmodules that may be used in accordance with aspects of the presentdisclosure may include electronic mail and contacts applications, wordprocessing applications, spreadsheet applications, databaseapplications, slide presentation applications, drawing or computer-aidedapplication programs, etc., and/or one or more components supported bythe systems described herein.

Furthermore, embodiments of the disclosure may be practiced in anelectrical circuit comprising discrete electronic elements, packaged orintegrated electronic chips containing logic gates, a circuit utilizinga microprocessor, or on a single chip containing electronic elements ormicroprocessors. For example, embodiments of the disclosure may bepracticed via a system-on-a-chip (SOC) where each or many of thecomponents illustrated in FIG. 13 may be integrated onto a singleintegrated circuit. Such an SOC device may include one or moreprocessing units, graphics units, communications units, systemvirtualization units and various application functionality all of whichare integrated (or “burned”) onto the chip substrate as a singleintegrated circuit. When operating via an SOC, the functionality,described herein, with respect to the capability of client to switchprotocols may be operated via application-specific logic integrated withother components of the computing device 1300 on the single integratedcircuit (chip). Embodiments of the disclosure may also be practicedusing other technologies capable of performing logical operations suchas, for example, AND, OR, and NOT, including but not limited tomechanical, optical, fluidic, and quantum technologies. In addition,embodiments of the disclosure may be practiced within a general-purposecomputer or in any other circuits or systems.

The computing device 1300 may also have one or more input device(s) 1312such as a keyboard, a mouse, a pen, a sound or voice input device, atouch or swipe input device, etc. The output device(s) 1314A such as adisplay, speakers, a printer, etc. may also be included. An output1314B, corresponding to a virtual display may also be included. Theaforementioned devices are examples and others may be used. Thecomputing device 1300 may include one or more communication connections1316 allowing communications with other computing devices 1350. Examplesof suitable communication connections 1316 include, but are not limitedto, radio frequency (RF) transmitter, receiver, and/or transceivercircuitry; universal serial bus (USB), parallel, and/or serial ports.

The term computer readable media as used herein may include computerstorage media. Computer storage media may include volatile andnonvolatile, removable and non-removable media implemented in any methodor technology for storage of information, such as computer readableinstructions, data structures, or program modules. The system memory1304, the removable storage device 1309, and the non-removable storagedevice 1310 are all computer storage media examples (e.g., memorystorage). Computer storage media may include RAM, ROM, electricallyerasable read-only memory (EEPROM), flash memory or other memorytechnology, CD-ROM, digital versatile disks (DVD) or other opticalstorage, magnetic cassettes, magnetic tape, magnetic disk storage orother magnetic storage devices, or any other article of manufacturewhich can be used to store information and which can be accessed by thecomputing device 1300. Any such computer storage media may be part ofthe computing device 1300. Computer storage media does not include acarrier wave or other propagated or modulated data signal.

Communication media may be embodied by computer readable instructions,data structures, program modules, or other data in a modulated datasignal, such as a carrier wave or other transport mechanism, andincludes any information delivery media. The term “modulated datasignal” may describe a signal that has one or more characteristics setor changed in such a manner as to encode information in the signal. Byway of example, and not limitation, communication media may includewired media such as a wired network or direct-wired connection, andwireless media such as acoustic, radio frequency (RF), infrared, andother wireless media.

FIGS. 14A and 14B illustrate a computing device or mobile computingdevice 1400, for example, a mobile telephone, a smart phone, wearablecomputer (such as a smart watch), a tablet computer, a laptop computer,and the like, with which aspects of the disclosure may be practiced.With reference to FIG. 14A, one aspect of a mobile computing device 1400for implementing the aspects is illustrated. In a basic configuration,the mobile computing device 1400 is a handheld computer having bothinput elements and output elements. The mobile computing device 1400typically includes a display 1405 and one or more input buttons 1410that allow the user to enter information into the mobile computingdevice 1400. The display 1405 of the mobile computing device 1400 mayalso function as an input device (e.g., a touch screen display). Ifincluded, an optional side input element 1415 allows further user input.The side input element 1415 may be a rotary switch, a button, or anyother type of manual input element. In alternative aspects, mobilecomputing device 1400 may incorporate more or less input elements. Forexample, the display 1405 may not be a touch screen in some aspects. Inyet another alternative aspect, the mobile computing device 1400 is aportable phone system, such as a cellular phone. The mobile computingdevice 1400 may also include an optional keypad 1435. Optional keypad1435 may be a physical keypad or a “soft” keypad generated on the touchscreen display. In various aspects, the output elements include thedisplay 1405 for showing a graphical user interface (GUI), a visualindicator 1431 (e.g., a light emitting diode), and/or an audiotransducer 1425 (e.g., a speaker). In some aspects, the mobile computingdevice 1400 incorporates a vibration transducer for providing the userwith tactile feedback. In yet another aspect, the mobile computingdevice 1400 incorporates input and/or output ports, such as an audioinput (e.g., a microphone jack), an audio output (e.g., a headphonejack), and a video output (e.g., a high-definition multimedia interface(HDMI) port) for sending signals to or receiving signals from anexternal source.

FIG. 14B is a block diagram illustrating the architecture of one aspectof computing device, a server, or a mobile computing device. That is,the mobile computing device 1400 can incorporate a system (1402) (e.g.,an architecture) to implement some aspects. The system 1402 canimplemented as a “smart phone” capable of running one or moreapplications (e.g., browser, e-mail, calendaring, contact managers,messaging clients, games, and media clients/players). In some aspects,the system 1402 is integrated as a computing device, such as anintegrated personal digital assistant (PDA) and wireless phone.

One or more application programs 1466 may be loaded into the memory 1462and run on or in association with the operating system 1464. Examples ofthe application programs include phone dialer programs, e-mail programs,personal information management (PIM) programs, word processingprograms, spreadsheet programs, Internet browser programs, messagingprograms, and/or one or more components supported by the systemsdescribed herein. The system 1402 also includes a non-volatile storagearea 1468 within the memory 1462. The non-volatile storage area 1468 maybe used to store persistent information that should not be lost if thesystem 1402 is powered down. The application programs 1466 may use andstore information in the non-volatile storage area 1468, such as e-mailor other messages used by an e-mail application, and the like. Asynchronization application (not shown) also resides on the system 1402and is programmed to interact with a corresponding synchronizationapplication resident on a host computer to keep the information storedin the non-volatile storage area 1468 synchronized with correspondinginformation stored at the host computer. As should be appreciated, otherapplications may be loaded into the memory 1462 and run on the mobilecomputing device 1400 described herein (e.g. a machine learning model1323 and a physio-realistic avatar video generator 1325, etc.).

The system 1402 has a power supply 1470, which may be implemented as oneor more batteries. The power supply 1470 might further include anexternal power source, such as an alternating current (AC) adapter or apowered docking cradle that supplements or recharges the batteries.

The system 1402 may also include a radio interface layer 1472 thatperforms the function of transmitting and receiving radio frequencycommunications. The radio interface layer 1472 facilitates wirelessconnectivity between the system 1402 and the “outside world,” via acommunications carrier or service provider. Transmissions to and fromthe radio interface layer 1472 are conducted under control of theoperating system 1464. In other words, communications received by theradio interface layer 1472 may be disseminated to the applicationprograms 1466 via the operating system 1464, and vice versa.

The visual indicator 1420 may be used to provide visual notifications,and/or an audio interface 1474 may be used for producing audiblenotifications via the audio transducer 1425. In the illustratedconfiguration, the visual indicator 1420 is a light emitting diode (LED)and the audio transducer 1425 is a speaker. These devices may bedirectly coupled to the power supply 1470 so that when activated, theyremain on for a duration dictated by the notification mechanism eventhough the processor 1460 and other components might shut down forconserving battery power. The LED may be programmed to remain onindefinitely until the user takes action to indicate the powered-onstatus of the device. The audio interface 1474 is used to provideaudible signals to and receive audible signals from the user. Forexample, in addition to being coupled to the audio transducer 1425, theaudio interface 1474 may also be coupled to a microphone to receiveaudible input, such as to facilitate a telephone conversation. Inaccordance with aspects of the present disclosure, the microphone mayalso serve as an audio sensor to facilitate control of notifications, aswill be described below. The system 1402 may further include a videointerface 1476 that enables an operation of an on-board camera to recordstill images, video stream, and the like.

A mobile computing device 1400 implementing the system 1402 may haveadditional features or functionality. For example, the mobile computingdevice 1400 may also include additional data storage devices (removableand/or non-removable) such as, magnetic disks, optical disks, or tape.Such additional storage is illustrated in FIG. 14B by the non-volatilestorage area 1468.

Data/information generated or captured by the mobile computing device1400 and stored via the system 1402 may be stored locally on the mobilecomputing device 1400, as described above, or the data may be stored onany number of storage media that may be accessed by the device via theradio interface layer 1472 or via a wired connection between the mobilecomputing device 1400 and a separate computing device associated withthe mobile computing device 1400, for example, a server computer in adistributed computing network, such as the Internet. As should beappreciated such data/information may be accessed via the mobilecomputing device 1400 via the radio interface layer 1472 or via adistributed computing network. Similarly, such data/information may bereadily transferred between computing devices for storage and useaccording to well-known data/information transfer and storage means,including electronic mail and collaborative data/information sharingsystems.

FIG. 15 illustrates one aspect of the architecture of a system forprocessing data received at a computing system from a remote source,such as a personal computer 1504, tablet computing device 1506, ormobile computing device 1508, as described above. Content displayed atserver device 1502 may be stored in different communication channels orother storage types.

In some aspects, one or more of a machine learning structure 1526, themachine learning model 1520, and the physio-realistic avatar videogenerator 1524, may be employed by server device 1502. The machinelearning model 1520 may be the same as or similar to the machinelearning models 144 and 442 as described with respect to, but notlimited to, at least FIGS. 1-14 of the present disclosure. Thephysio-realistic avatar video generator 1524 may be the same as orsimilar to the physio-realistic video generator 304 with respect to, butnot limited to, at least FIGS. 1-14 of the present disclosure. Themachine learning structure 1526 may be the same as or similar to theend-to-end learning model 136 and 404 as described with respect to, butnot limited to, at least FIGS. 1-14 of the present disclosure. Theserver device 1502 may provide data to and from a client computingdevice such as a personal computer 1504, a tablet computing device 1506and/or a mobile computing device 1508 (e.g., a smart phone) through anetwork 1512. By way of example, the computer system described above maybe embodied in a personal computer 1504, a tablet computing device 1506and/or a mobile computing device 1508 (e.g., a smart phone). Any ofthese embodiments of the computing devices may obtain content from thestore 1516, in addition to receiving graphical data useable to be eitherpre-processed at a graphic-originating system, or post-processed at areceiving computing system. The content store may include thephysiological model repository 1532, the physio-realistic avatar videorepository 1536, and/or a physiological measurement 1540.

FIG. 15 illustrates an exemplary mobile computing device 1500 that mayexecute one or more aspects disclosed herein. In addition, the aspectsand functionalities described herein may operate over distributedsystems (e.g., cloud-based computing systems), where applicationfunctionality, memory, data storage and retrieval and various processingfunctions may be operated remotely from each other over a distributedcomputing network, such as the Internet or an intranet. User interfacesand information of various types may be displayed via on-board computingdevice displays or via remote display units associated with one or morecomputing devices. For example, user interfaces and information ofvarious types may be displayed and interacted with on a wall surfaceonto which user interfaces and information of various types areprojected. Interaction with the multitude of computing systems withwhich embodiments of the invention may be practiced include, keystrokeentry, touch screen entry, voice or other audio entry, gesture entrywhere an associated computing device is equipped with detection (e.g.,camera) functionality for capturing and interpreting user gestures forcontrolling the functionality of the computing device, and the like.

The phrases “at least one,” “one or more,” “or,” and “and/or” areopen-ended expressions that are both conjunctive and disjunctive inoperation. For example, each of the expressions “at least one of A, Band C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “oneor more of A, B, or C,” “A, B, and/or C,” and “A, B, or C” means Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, or A, B and C together.

The term “a” or “an” entity refers to one or more of that entity. Assuch, the terms “a” (or “an”), “one or more,” and “at least one” can beused interchangeably herein. It is also to be noted that the terms“comprising,” “including,” and “having” can be used interchangeably.

The term “automatic” and variations thereof, as used herein, refers toany process or operation, which is typically continuous orsemi-continuous, done without material human input when the process oroperation is performed. However, a process or operation can beautomatic, even though performance of the process or operation usesmaterial or immaterial human input, if the input is received beforeperformance of the process or operation. Human input is deemed to bematerial if such input influences how the process or operation will beperformed. Human input that consents to the performance of the processor operation is not deemed to be “material.”

Any of the steps, functions, and operations discussed herein can beperformed continuously and automatically.

The exemplary systems and methods of this disclosure have been describedin relation to computing devices. However, to avoid unnecessarilyobscuring the present disclosure, the preceding description omitsseveral known structures and devices. This omission is not to beconstrued as a limitation. Specific details are set forth to provide anunderstanding of the present disclosure. It should, however, beappreciated that the present disclosure may be practiced in a variety ofways beyond the specific detail set forth herein.

Furthermore, while the exemplary aspects illustrated herein show thevarious components of the system collocated, certain components of thesystem can be located remotely, at distant portions of a distributednetwork, such as a local area network (LAN) and/or the Internet, orwithin a dedicated system. Thus, it should be appreciated, that thecomponents of the system can be combined into one or more devices, suchas a server, communication device, or collocated on a particular node ofa distributed network, such as an analog and/or digitaltelecommunications network, a packet-switched network, or acircuit-switched network. It will be appreciated from the precedingdescription, and for reasons of computational efficiency, that thecomponents of the system can be arranged at any location within adistributed network of components without affecting the operation of thesystem.

Furthermore, it should be appreciated that the various links connectingthe elements can be wired or wireless links, or any combination thereof,or any other known or later developed element(s) that is capable ofsupplying and/or communicating data to and from the connected elements.These wired or wireless links can also be secure links and may becapable of communicating encrypted information. Transmission media usedas links, for example, can be any suitable carrier for electricalsignals, including coaxial cables, copper wire, and fiber optics, andmay take the form of acoustic or light waves, such as those generatedduring radio-wave and infra-red data communications.

While the flowcharts have been discussed and illustrated in relation toa particular sequence of events, it should be appreciated that changes,additions, and omissions to this sequence can occur without materiallyaffecting the operation of the disclosed configurations and aspects.

Several variations and modifications of the disclosure can be used. Itwould be possible to provide for some features of the disclosure withoutproviding others.

In yet another configurations, the systems and methods of thisdisclosure can be implemented in conjunction with a special purposecomputer, a programmed microprocessor or microcontroller and peripheralintegrated circuit element(s), an ASIC or other integrated circuit, adigital signal processor, a hard-wired electronic or logic circuit suchas discrete element circuit, a programmable logic device or gate arraysuch as PLD, PLA, FPGA, PAL, special purpose computer, any comparablemeans, or the like. In general, any device(s) or means capable ofimplementing the methodology illustrated herein can be used to implementthe various aspects of this disclosure. Exemplary hardware that can beused for the present disclosure includes computers, handheld devices,telephones (e.g., cellular, Internet enabled, digital, analog, hybrids,and others), and other hardware known in the art. Some of these devicesinclude processors (e.g., a single or multiple microprocessors), memory,nonvolatile storage, input devices, and output devices. Furthermore,alternative software implementations including, but not limited to,distributed processing or component/object distributed processing,parallel processing, or virtual machine processing can also beconstructed to implement the methods described herein.

In yet another configuration, the disclosed methods may be readilyimplemented in conjunction with software using object or object-orientedsoftware development environments that provide portable source code thatcan be used on a variety of computer or workstation platforms.Alternatively, the disclosed system may be implemented partially orfully in hardware using standard logic circuits or very large scaleintegration (VLSI) design. Whether software or hardware is used toimplement the systems in accordance with this disclosure is dependent onthe speed and/or efficiency requirements of the system, the particularfunction, and the particular software or hardware systems ormicroprocessor or microcomputer systems being utilized.

In yet another configuration, the disclosed methods may be partiallyimplemented in software that can be stored on a storage medium, executedon programmed general-purpose computer with the cooperation of acontroller and memory, a special purpose computer, a microprocessor, orthe like. In these instances, the systems and methods of this disclosurecan be implemented as a program embedded on a personal computer such asan applet, JAVA® or computer-generated imagery (CGI) script, as aresource residing on a server or computer workstation, as a routineembedded in a dedicated measurement system, system component, or thelike. The system can also be implemented by physically incorporating thesystem and/or method into a software and/or hardware system.

The disclosure is not limited to standards and protocols if described.Other similar standards and protocols not mentioned herein are inexistence and are included in the present disclosure. Moreover, thestandards and protocols mentioned herein, and other similar standardsand protocols not mentioned herein are periodically superseded by fasteror more effective equivalents having essentially the same functions.Such replacement standards and protocols having the same functions areconsidered equivalents included in the present disclosure.

In accordance with at least one example of the present disclosure, amethod for generating video sequences including physio-realistic avatarsis provided. The method may include receiving an albedo for an avatar,modifying a sub-surface skin color associated with the albedo based onphysiological data associated with physiologic characteristic, renderingan avatar based on the albedo and the modified sub-surface skin color,and synthesizing a frame of video, the frame of video including theavatar.

In accordance with at least one aspect of the above method, thephysiological data varies with time and the method further includesmodifying the sub-surface skin color associated with the albedo based onthe physiological data at a first time, rendering the avatar based onthe albedo and the modified sub-surface skin color associated with thephysiological data at the first time, synthesizing a first frame ofvideo, the first frame of video including the avatar rendered based onthe albedo and the modified sub-surface skin color associated with thephysiological data at the first time, modifying the sub-surface skincolor associated with the albedo based on the physiological data at asecond time, rendering the avatar based on the albedo and the modifiedsub-surface skin color associated with the physiological data at thesecond time, and synthesizing a second frame of video, the second frameof video including the avatar rendered based on the albedo and themodified sub-surface skin color associated with the physiological dataat the second time. In accordance with at least one aspect of the abovemethod, the method includes modifying a plurality of color channels withweighting factors specific to the physiological data, modifying thesub-surface skin associated with the albedo with the plurality of colorchannels. In accordance with at least one aspect of the above method,the method includes varying a sub-surface radii for one or more of theplurality of color channels based on the weighting factors specific tothe physiological data. In accordance with at least one aspect of theabove method, the method includes training a machine learning model witha plurality of synthesized frames of that include the avatar. Inaccordance with at least one aspect of the above method, the methodincludes training the machine learning model with a plurality of videosincluding human subjects. In accordance with at least one aspect of theabove method, the method includes receiving a plurality of video framesdepicting a human subject, and recovering a physiological signal basedon the trained machine learning model. In accordance with at least oneaspect of the above method, the frame of video includes the avatar infront of a dynamic background. In accordance with at least one aspect ofthe above method, the method includes receiving the physiological datafrom a requesting entity, synthesizing the frame of video including theavatar substantially in real-time, and providing the frame of video tothe requesting entity. In accordance with at least one aspect of theabove method, the physiological characteristic is blood volume pulse. Inaccordance with at least one aspect of the above method, the methodincludes labeling a video segment including the synthesized frame ofvideo with a training label specific to the physiologic characteristic.

In accordance with at least one example of the present disclosure, asystem for training a machine learning model using video sequencesincluding physio-realistic avatars is provided. The system may include aprocessor, and memory storing instructions, which when executed by theprocessor, cause the processor to receive a request from a requestingentity to train a machine learning model to detect a physiologicalcharacteristic, receive a plurality of video segments, wherein one ormore of the video segments includes a synthetic physio-realistic avatargenerated with the physiological characteristic, train the machinelearning model with the plurality of video segments, and provide atrained model to the requesting entity.

In accordance with at least one aspect of the above system, theinstructions, which when executed by the processor, cause the processorto receive a second plurality of video segments, wherein one or morevideo segments included in the second plurality of video segmentsdepicts a human with the physiological characteristic, and train themachine learning model with the plurality of video segments and thesecond plurality of video segments. In accordance with at least oneaspect of the above system, the physiological characteristic is a bloodvolume pulse. In accordance with at least one aspect of the abovesystem, the one or more of the plurality of video segments are labeledwith a training label based on the physiological characteristic. Inaccordance with at least one aspect of the above system, theinstructions, which when executed by the processor, cause the processorto receive a second video segment, identify a physiologicalcharacteristic from the second video segment using the trained model,and provide an assessment of the physiological characteristic to therequesting entity.

In accordance with at least one example of the present disclosure, acomputer-readable media is provided. The computer-readable mediaincludes instructions, which when executed by a processor, cause theprocessor to receive a request to recover a physiological characteristicfrom a video segment, obtain a machine learning model trained withtraining data that includes physio-realistic avatars generated with thephysiological characteristic, receive a video segment, identify ameasure associated with the physiological characteristic from the videosegment using the trained machine learning model, and provide anassessment of the physiological characteristic to the requesting entitybased on the measure.

In accordance with at least one example of the above computer-readablemedia, the instructions, which when executed by the processor, cause theprocessor to receive an albedo for an avatar, modify a sub-surface skincolor associated with the albedo based on physiological data associatedwith the physiologic characteristic, render an avatar based on thealbedo and the modified sub-surface skin color, synthesize a frame ofvideo, the frame of video including the avatar, and train the machinelearning model with the synthesized frame of video. In accordance withat least one example of the above computer-readable media, theassessment of the physiological characteristic is a pulse rate. Inaccordance with at least one example of the above computer-readablemedia, the received video segment depicts a human subject.

At least one aspect of the above system may include where theinstructions cause the processor to utilize a tree-based classifier toidentify the covariates impacting the quality metric based on featuresincluded in the first telemetry data and the second telemetry data. Atleast one aspect of the above system may include where the instructionscause the processor to stratify the first and second group of devicesusing a subset of the identified covariates that are greater than athreshold. At least one aspect of the above system may include where theinstructions cause the processor to provide the quality metric to adisplay device in proximity to the predicted quality metric.

The present disclosure, in various configurations and aspects, includescomponents, methods, processes, systems and/or apparatus substantiallyas depicted and described herein, including various combinations,subcombinations, and subsets thereof. Those of skill in the art willunderstand how to make and use the systems and methods disclosed hereinafter understanding the present disclosure. The present disclosure, invarious configurations and aspects, includes providing devices andprocesses in the absence of items not depicted and/or described hereinor in various configurations or aspects hereof, including in the absenceof such items as may have been used in previous devices or processes,e.g., for improving performance, achieving ease, and/or reducing cost ofimplementation.

1. A method for generating video sequences including physio-realisticavatars, the method comprising: receiving an albedo for an avatar;modifying a sub-surface skin color associated with the albedo based onphysiological data associated with physiologic characteristic; renderingan avatar based on the albedo and the modified sub-surface skin color;and synthesizing a frame of video, the frame of video including theavatar.
 2. The method of claim 1, wherein the physiological data varieswith time, the method further comprising: modifying the sub-surface skincolor associated with the albedo based on the physiological data at afirst time; rendering the avatar based on the albedo and the modifiedsub-surface skin color associated with the physiological data at thefirst time; synthesizing a first frame of video, the first frame ofvideo including the avatar rendered based on the albedo and the modifiedsub-surface skin color associated with the physiological data at thefirst time; modifying the sub-surface skin color associated with thealbedo based on the physiological data at a second time; rendering theavatar based on the albedo and the modified sub-surface skin colorassociated with the physiological data at the second time; andsynthesizing a second frame of video, the second frame of videoincluding the avatar rendered based on the albedo and the modifiedsub-surface skin color associated with the physiological data at thesecond time.
 3. The method of claim 1, further comprising: modifying thephysiological data with weighting factors specific to the physiologicaldata; and modifying the sub-surface skin associated with the albedo withthe modified physiological data.
 4. The method of claim 3, furthercomprising varying a sub-surface radii for one or more of the pluralityof color channels based on the weighting factors specific to thephysiological data.
 5. The method of claim 1, further comprisingtraining a machine learning model with a plurality of synthesized framesof that include the avatar.
 6. The method of claim 5, further comprisingtraining the machine learning model with a plurality of videos includinghuman subjects.
 7. The method of claim 6, further comprising: receivinga plurality of video frames depicting a human subject; and recovering aphysiological signal based on the trained machine learning model.
 8. Themethod of claim 1, wherein the frame of video includes the avatar infront of a dynamic background.
 9. The method of claim 1, furthercomprising: receiving the physiological data from a requesting entity;synthesizing the frame of video including the avatar substantially inreal-time; and providing the frame of video to the requesting entity.10. The method of claim 1, wherein the physiological characteristic isblood volume pulse.
 11. The method of claim 1, further comprisinglabeling a video segment including the synthesized frame of video with atraining label specific to the physiologic characteristic.
 12. A systemfor training a machine learning model using video sequences includingphysio-realistic avatars, the system comprising: a processor; and memorystoring instructions, which when executed by the processor, cause theprocessor to: receive a request from a requesting entity to train amachine learning model to detect a physiological characteristic; receivea plurality of video segments, wherein one or more of the video segmentsincludes a synthetic physio-realistic avatar generated with thephysiological characteristic; train the machine learning model with theplurality of video segments; and provide a trained model to therequesting entity.
 13. The system of claim 12, further comprisinginstructions, which when executed by the processor, cause the processorto: receive a second plurality of video segments, wherein one or morevideo segments included in the second plurality of video segmentsdepicts a human with the physiological characteristic; and train themachine learning model with the plurality of video segments and thesecond plurality of video segments.
 14. The system of claim 12, whereinthe physiological characteristic is a blood volume pulse.
 15. The systemof claim 12, wherein one or more of the plurality of video segments arelabeled with a training label based on the physiological characteristic.16. The system of claim 12, further comprising instructions, which whenexecuted by the processor, cause the processor to: receive a secondvideo segment; identify a physiological characteristic from the secondvideo segment using the trained model; and provide an assessment of thephysiological characteristic to the requesting entity.
 17. Acomputer-readable media including instructions, which when executed by aprocessor, cause the processor to: receive a request to recover aphysiological characteristic from a video segment; obtain a machinelearning model trained with training data that includes physio-realisticavatars generated with the physiological characteristic; receive a videosegment; identify a measure associated with the physiologicalcharacteristic from the video segment using the trained machine learningmodel; and provide an assessment of the physiological characteristic tothe requesting entity based on the measure.
 18. The computer-readablemedia of claim 17, wherein the instructions, which when executed by theprocessor, cause the processor to: receive an albedo for an avatar;modify a sub-surface skin color associated with the albedo based onphysiological data associated with the physiologic characteristic;render an avatar based on the albedo and the modified sub-surface skincolor; synthesize a frame of video, the frame of video including theavatar; and train the machine learning model with the synthesized frameof video.
 19. The computer-readable media of claim 17, wherein theassessment of the physiological characteristic is a pulse rate.
 20. Thecomputer-readable media of claim 17, wherein the received video segmentdepicts a human subject.